1. Technical Field
This disclosure relates generally to a method for monitoring one or more turbine engine rotor blades as a function of time.
2. Background Information
A typical non-interference stress measurement system (NSMS) monitors one or more turbine engine rotor blades to determine various rotor blade properties such as actual rotor blade time of arrival, rotor blade deflection, etc. The NSMS may estimate, for example, that a first blade arrives at a particular measurement location when a voltage signal provided by a corresponding blade position sensor rises above a triggering threshold. A difference between the estimated time of arrival and a predicted time of arrival may be multiplied by a known rotational velocity of the first blade to determine the first blade deflection. The predicted time of arrival corresponds to a point in time when the first blade should arrive at the measurement location absent any blade deflection. Various additional rotor blade properties such as rotor blade stress may be calculated based on the estimated time of arrival and/or the blade deflection.
Noise in the voltage signal provided by the blade position sensor may introduce error into the estimated time of arrival and, thus, the blade deflection measurement. The noise, for example, may cause a premature or delayed rise of the signal above the triggering threshold. Such noise therefore can disadvantageously reduce NSMS accuracy and precision.